Men who watch porn excessively are risking permanently damaging their sex lives.

New research, presented at the 112th Annual Scientific Meeting of the American Urological Association, has found that watching too much porn can cause sexual dysfunction.

Even more disturbingly, 4% of male respondents claimed that they actually prefer masturbating to pornography rather than having sex with a real-life partner.

Meanwhile, more than 20% of the men admitted to watching porn three to five times every week,

Dr Matthew Christman, who led the study, explained: “The rates of organic causes of erectile dysfunction in this age cohort are extremely low, so the increase in erectile dysfunction that we have seen over time for this group needs to be explained.

“We believe that pornography use may be one piece to that puzzle.

“They believe they’re supposed to be able to do what goes on in these movies, and when they can’t it causes a great deal of anxiety,” he added.

How much is too much?